11807609-oil spill block 35-36-draft report

8/13/2019 11807609-Oil Spill Block 35-36-Draft Report

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Oil exploration off the coast of

Peru Block Z-35 and Z-36

Assessment of spills using M!" 3

model s#stem

$raft %$ &eport

Draft ReportMay 2011


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Oil exploration off the coast ofPeru Block Z-35 and Z-36

Assessment of spills using M!" 3

model s#stem

Draft HD Report

Agern All 5

DK-2970 Hrsholm, Denmark

Tel: +45 4516 9200

a!: +45 4516 9292

"n#$#als: mm%msl

e-ma#l: &h#'&h#(&k

)e*: (&h#(&k

l#en$

)alsh er. /(A(l#en$s reresen$a$#e

3

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#l e!lora$#on o $he oas$ o er8 lok ;-


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CONTENTS

0 /G??AB A=D =EG/"=((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((1

1 "=TBDGT"=((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((1

2 DCB"T"= THC /"TC(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((1

< ABAH((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((10>5


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0 SUMMARY AND CONCLUSION

New oil explorations off the coast of Peru around Block Z-35 and Z-36 require theassessment of potential spills in terms of hydrocarbon barrels and drillin mud!

"n this context #alsh Per$ %!&!has commissioned '(" to make an assessment of spills

usin the )"*+ by '(" software!

,he scope of work is diided into two parts.

+stablishment and erification of a )"*+ 3 hydrodynamic model of the area around

Block Z / 35 and Z-36 for summer0 winter0 +l Ni1o and 2a Ni1a conditions!

&ssessment of potential spills utilisin the particle trackin and spill analysis model

within )"*+ 30 hereundero &ssessin oil spills and fate of drill mud and cuttins and associated

particles attached and water soluble toxic substances4 durin drill operations

o &ssessin spreadin and fate of accidental oil spills durin the operation of

producer wells

,he main focus of the model alidation has been a proper representation of the oerall

current system of the Peruian coast! "n addition0 the hydrodynamic model includes a

representation of the tidal currents! ,hus the model can capture seasonal as well as daily

flow fluctuations! ,he latter is likewise important when tracin spills around the

production wells! &lthouh the model has a finer resolution in the area between Block Z

/ 35 and Z-36 and the coastline0 further refinements may be required to study

circulation in sensitie areas in more details!

,he hydrodynamic model was set-up for winter and summer conditions two periods of

months4 in 778 and 779 respectiely0 includin summer and winter periods and at

the same time also +l Ni1o and 2a Ni1a eents! :enerally0 the model captures the

temperature patterns obsered by satellite! ,he model results hae further been

compared with &';P current measurements carried out in ctober 7=7!

1954>0>5


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1 INTRODUCTION

New oil explorations off the coast of Peru around Block Z-35 and Z-36 ?iure =-=4require the assessment of potential spills in terms of hydrocarbon barrels and drillin

mud!

,he hydraulic conditions at the coastal reion of Peru are complex! ,he reion is

dominated by upwellin of relatiely cold water durin the preailin winds from south!

,o be able to describe the associated circulation it is necessary to set up a 3-'

hydrodynamic model of the coastal area around Block Z-35 and Z-36! & subsequent

assessment of spreadin of potential spills requires the use of a particle trackin model

combined with a description of the deradation processes the so-called weatherin

processes4!

"n this context #alsh Per$ %!&! requested '(" to make an assessment of spills usin the

)"*+ by '(" software!

,he scope of work is laid down in a proposal prepared by '("0 dated ?ebruary0 6

7=70 and comprises.

+stablishment and erification of a )"*+ 3 hydrodynamic model of the area around

Block Z-35 and Z-36 ?iure = -=4 for summer0 winter0 +l Ni1o and 2a Ni1a

conditions!

&ssessment of potential spills utilisin the particle trackin and spill analysis model

within )"*+ 30 hereundero &ssessin oil spills and fate of drill mud and cuttins and associated

particles attached and water soluble toxic substances4 durin drill operations

o &ssessin spreadin and fate of accidental oil spills durin the operation of

producer wells

#alsh Per$ %!&!has proided all releant information@s such as local bathymetry0

&';P measurements and0 wind statistics!

1954>0>5


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Figure 1-1 Location of block Z-35 and Z-36 (drill locations are marked green)

1954>0>5


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2 DECRIPTION OF THE SITE

,he hydraulic conditions in the area are complicated and dominated by the Peruian;urrent %ystem P;%40 see fiure -=! "n the coastal area the Peruian ;urrent %ystem

consists of a northward flowin surface current known as the Peruian ;hilean ;ostal

;urrent P;;;4 or the (umbolt ;urrent! Below the P;;; a current of relatiely cold0

nutrient rich and anoxic water called the Peruian ;oastal Ander ;urrent P;A;4 flows

towards south!

,he P;% is partly drien by a southerly wind parallel to the coast from 3 % towards

equator! ,his wind is the south east trade wind bein deflected northward by the &ndes

)ountains and a sea breeCe! 'ue to the ;oriolis force the P;;; is dierted towards west

called the +kman transport4 thereby drain the cold nutrient rich water from the deeper

P;A; to the surface at the coast and out to the sea0 see ?iure -!,his upwellin ofwater is common alon the coast of ;hile and Peru from about % until about 3 %0 ref!

0 eneratin one of the most productie waters in the sea!

Figure 2-2 Principle of te Peru!ian "urrent #$stem

1954>0>5


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,he warm surface layer is about 7-67 m thick0 but may be deeper durin +l NiDo

eents and situations with costal trapped lon waes enerated by *elin waes4

passin from equator to the poles!

,he southern winds and thereby the upwellin seem to be most stable and frequentdurin winter!

,he aboe description of the hydraulic conditions in the Pacific and the coastal waters

may be disrupted by *elin waes of warm water traellin from the western part of the

Pacific towards east hittin the coasts of +cuador and Peru!

,his wae may trier an +l NiDo eent which may last a year! 'urin +l NiDo with its

associated *elin waes the warm surface layer becomes thicker and the upwellin has

a smaller associated nutrient content!

"n case of accidental spills from Block Z-35 and Z-36 the main concern will be sensitieresources alon the coast line likely to be effected by the spill!

1954>0>5


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3 APPROACH

,he obEectie of the modellin is to assess the impact of potential spills in terms ofhydrocarbon barrels and drillin mud under specific meteoroloical and ocean current

conditions!

"n order to describe the associated circulation it is necessary to set up a 3- '

hydrodynamic model of the coastal area around Block Z-35 and Z-36! ,he assessment

of spreadin of potential spills requires the use of a particle trackin model combined

with a description of the deradation processes the so-called weatherin processes4!

?urthermore0 the spreadin of mud particles and dissoled toxic substances require the

use of adection and sediment transport models! ,he )"*+ 3 model complex

deeloped by '(" and applied worldwide in marine and coastal areas4 comprises all of

the aboe features and has been applied for the present study!

,he Block Z-35 and Z-36 coers the area comprised between the coast and 87 # of

lonitude and between F % and == % of latitude! (oweer0 the hydrodynamic model

will extend much further alon the coast and off shore in order to be able to capture the

complex circulation and of course the sensitie areas in the icinity of the potential spill

areas!

,he spill scenarios comprise.

'umpin of drill cuttins. 5 tons instantaneously or 57 tonnes released oer one

hour

'umpin of drillin mud. 57 barrels instantaneously and 577 barrels oer one

hour

&ccidental oil spill. =7 barrels oer 67 minutes0 =777 barrels oer 67 minutes

and =777 barrels oer =87 minutes! "n this context it is assumed that the spills

take place at the sea surface

Geardin the spills0 different model approaches as outlined below will be applied.

Drill cuttings! ;uttins are represented by coarse material that will deposit quickly in

the area around the drill ri! Based on typical flow elocities an assessment of the

horiContal distance from the ri by assumin some rain diameter and fall elocity4

will be made! ,he calculations are supported by simulations utiliCin the )"*+ 3 P&

particle model! ,hus0 the results shall be considered as typical spreadin distances!

?urthermore0 an assessment of toxic substances attached to the cuttins whether the

concentrations are considered harmful to the sea habitats4 can be made based on

aailable information reardin toxicity! ,he latter is important in order to assess the

potential ecoloical impacts!

Water-based drilling muds! ,he toxic compounds associated with the drillin mud

will either stick to the fine mud particle and settle to the ocean floor and they could be

1 DH"


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harm full to benthic habitats if they are bioaailable4 or they will be totally dissoled

?or this reason the spill of drill mud is diided into two assessments.

,he transport and dilution of soluble substances! ,he results comprise predicted

chemical concentrations in the water column! ,hese concentrations arecompared with the PN+; for the water phase!

,he spreadin0 deposition and re-suspension of fine particles! ,he settlin is

modelled iin predicted thickness layers of solid drillin muds! ?urthermore0

the concentration of the chemicals in the pore water is estimated and compared

with the PN+; for the water phase!

?or this assessment0 information on the amount of the dischared mud0 the amount of

each chemical oin to the water column0 respectiely to the solid phase is needed!

#ithin Block Z-35 and Z-36 a total of 36 wells are comprised by the presentinestiation! (oweer0 in order to reduce the amount of simulation the modellin will

focus on two selected locations within each block! 2ocations closest to the coastline will

most likely be the most critical in case of accidental spills!

Oil spill! &ll thouh the oil spill simulations are fully 3-'0 only the transport and fate

of the oil on the surface has been assessed! ,he simulations will be prepared for selected

wells only two locations in each Block is foreseen as this is considered sufficient in

order to assess the impact areas4!

"n order to be able to access the risk of an oil spill reachin any ien area as a

percentae0 a lare number of oil spill scenarios =77H for each season4 will besimulated! ,he time of spillin and hence the met ocean conditions in terms of

weather0 waes and currents4 will be selected at random within the two periods utilisin

a )onte ;arlo principle! Based on the lare number of simulations a statistical analysis

will produce risk maps showin probability cures of reachin specific locations alon

the coast or other sensitie areas! Gesults will also comprise oil thickness and mass0

stranded oil and risk maps showin the influence area down to 5 or = I probability of

reachin a certain location4!

3.1 Hydrodynami mod!""in#

,he )"*+ 3 hydrodynamic model simulates unsteady flow takin into account density

ariations0 bathymetry and external forcin such as meteoroloy0 tidal eleations0

currents and other hydroraphic conditions! ,he hydrodynamic model proides the

platform for the oil spill module!

,he hydrodynamic modellin system is based on the numerical solution of the three-

dimensional incompressible Geynolds aeraed Naier-%tokes equations subEect to the

assumptions of Boussinesq and usin an assumption of hydrostatic pressure! ,hesolution to the equations are soled by finite olume techniques with the ariables

defined on a flexible mesh horiContally and a combined stretched J-C discretiCation in

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the ertical! ,he flexible mesh proides the possibility of refinin areas of special

interestK namely a reion between the potential spill locations in block Z-35 and Z-36

and the coast line!

,he (' model will be set up for two periods of months comprisin flow conditions

correspondin to summer0 winter and also +l Ni1o and 2a Ni1a conditions! ,he

necessary model initial and boundary conditions in terms of water leels0 salinity and

temperature for the periods hae been established from arious data sources such as

the P%L3 lobal data from the )ercator >perational %ystem!

,he model is subsequently erified based on the aailable data! ,hese data mainly

comprise satellite pictures of sea surface water temperature and selected measured data

on currents and water leels!

3.2 Oi" $%i"" mod!""in#

3.3 Eo&o'ii&y o( &)! )!mia"$ in dri"" m*d

Pendin

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+ DATA AND DATA ANALYSIS

Geleant model data are collected for the desin periods listed in ,able -=and ,able-0 which proide an oeriew of the arious types of data and the source for

information! ,wo periods were selected to coer two possible combinations of +l

Ni1oM2a Ni1a and summerMwinter conditions!

Period =. =


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)a$er leel ?CBATB CA= mo&el an& $#&al re$#ons

rom TCL%ose#&on al$#me$r &a$a( The

al$#me$r &a$a has *een 8se& $o al8la$e a se$ o

glo*al a$er leel $#&al ons$#$8en$, rom h#h $he

$#&al *o8n&ar on$#ons are al8la$e&(

8rren$s ?CBATB CA= mo&el an& AD

meas8remen$s #n @8l A8g8s$ -2010 ro#&e& *

)alsh er. /(A

/al#n#$ M

Temera$8re

?CBATB CA= mo&el(

)#n& see& M re$#on =C-=AA $hree ho8rl al8es ro#&e& * DH"

an& s$a$#s$#al &a$a rom oas$al s$a$#ons Iro#&e&

* )alsh er. /(A(J(

)aes N)a$er oreas$ * DH"O rom DH"s glo*al ae

mo&el

A#r $emera$8re, an& lo8ness =C-=AA

/a$ell#$e #mages o a$er

$emera$8re or mo&el

er##a$#on

=A/A I?D"/ AP8a //T #magesJ

h$$:%%mos(gs(nasa(go%

Spilldata

#l an& m8& s#lls #n $erms o

amo8n$ an& hara$er#s$#s(

ro#&e& * )alsh er. /(A( IenngJ

+.1 M!&,o!an da&a

,he )+G;&,>G >;+&N data comprise daily aerae alues of temperature0 salinity0

elocity A meridional40 elocity Conal4 and sea surface eleation within the entire

domain comprised by 85# to F8# and 7% to %! 'ata are proided for the entire

full domain at a =M horiContal resolution!

"nformation on tide is established usin the tidal prediction tool based on an inersion

of the ,>P+OMPoseidon altimetry data! ,hus0 the tidal data are based on the

astronomical tidal constituents only and do not include the pressure and wind set-up0 the

latter of which is0 howeer0 included in the )+G;&,>G >;+&N data! ,he response to

lare scale atmospheric pressure radients is included ia assumin a static inerse

barometer effect at the boundary usin the pressure from the :?% wind field! ,he model

water leel boundary used in the model is thus the sum of the tidal prediction0

atmospheric pressure and the wind set-up! &n example of the water leel boundary

?ebruary 7784 at a central point alon the western seaward boundary F8# to 85#4 is

shown in ?iure -!

?iure -5proides wind roses as extracted from the :?%- lobal forecast system

wind speed and direction ia N;+P- N>&&4 3-hourly data close to the land stations

2 DH"
http://modis.gsfc.nasa.gov/http://modis.gsfc.nasa.gov/


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;himbote and Pacasmayo! ,he statistics is based on the two desin periods in 778 and

779 respectiely! &ccordin to these lobal data the preailin wind direction is %-

%#! "n 778 the direction is more %-%+ at Pascamayo! %tatistical data hae been

proided for the two land stations coerin the years =9F9 to 779! &t both stations the

dominant direction is %+ =7 derees4 which is somewhat in contradiction to theN;+P-N>&& data! ,he main difference is belieed to be due to the fact that the lobal

weather data from N;+P-N>&& does not reflect the offshore sea breeCe! ,his

discrepancy is howeer only considered important close to land! ;onsequently the

lobal data are found adequate for the model simulation and assessment of oil spill

spreadin on the surface! )oreoer0 the area described in section 5 is of the same order

of manitude as the synoptic meteoroloical ariability0 and the N;+P-N>&& wind

forcin is therefore used instead of extrapolatin the measurements to the entire domain!

Figure %-% ater le!el !ariation at a central point along te +estern model boundar$

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Figure %-5 ind roses establised from 4F#- global forecast s$stem (/".P- /& data ) near te land stations at "imbote and Pacasma$o,

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%,2 rill "uttings and rill ud

Pending

%,3 &il properties

Pending

15%78753,doc 1 9'


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5 9$drod$namic odel set-up

The model set-up comprises the offshore region around block Z-35 and Z-36 bounded

by longitude 85W to 8W and latitude !"# to !#$ The resolution %aries bet&een 3"

to ! km &here the latter the finer resolution is pro%ided in the region bet&een the

potential spill locations in block Z-35 and Z-36 and the coastline$ ' %arying %ertical

resolution &ith !" layers has been applied starting &ith (-! meters near the surface and

increasing in layer thickness up to (""" m$The finer resolution in the upper part of the

&ater column ensures that the surface currents and %ertical mi)ing can be resol%ed

satisfactorily$ The model area and hori*ontal resolution are depicted in +igure 5 -6$

+igure 5 -pro%ides the model bathymetry, and+igure 5 -8pro%ide an o%er%ie& of

the a%ailable data utili*ed during the model construction$

The setup has three open boundaries as seen in +igure 5 - ' northern, a southern

and a &estern boundary$.oth the tidal, &ind dri%en and regional ocean currents are simulated in the

oceanographic hydrodynamic model$

.oundary and initial conditions in terms of le%els, mean currents, temperature and

salinity boundary are e)tracted from the /012'T1 20'4 data$ #ubseuently tidal

boundary conditions are e)tracted from global tidal constituents prepared by

TP07Poseidon and superposed to the /012'T1 boundary conditions$

n all open boundaries these superposed &ater le%els and depth a%eraged currents are

applied %ia +lathers 91ef 737: non-reflecti%e boundary condition formulation 9+lather

(;6: and prescribed 3< baroclinic %elocities and ad%ecti%e temperature and salinity

conditions are further used$

Wind and pressure fields as pro%ided %ia 420P-4'' data are applied in order to

represent &ind shear stress on the sea surface and atmospheric pressure gradients$ =n

addition 420P-4'' data for air temperature, relati%e humidity and cloudiness are

used to describe the heat e)change bet&een the sea surface and the atmosphere &ithin

the model area$

15%78753,doc 2 9'


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Figure 5-6 odel area: resolution (left) and a location of +ells +itin ;lock Z-35 and Z-35 (rigt),

Figure 5-< odel bat$metr$

Figure 5-7 #ources regarding model bat$metr$ .&P& (offsore): "-P (along te coast) and local 4'# data from als Per= #,,

15%78753,doc 3 9'


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6 results

The follo&ing sections pro%ide model results and assessments for the different tasksstarting &ith the %erification of the hydrodynamic ocean model$

6,1 9$drod$namic model

The model has been set-up for &inter and summer conditions including 0l 4i>o and ?a

4i>a e%ents for the periods specified in Table @ -($ /odel parameters ha%e been

adAusted in order to match e)isting satellite obser%ations of sea surface temperatures$

/odel results for selected days are pro%ided in figure .-( through figure .-3$

=n+igure 6 -;through+igure 6 -((is sho&n model simulated &ater le%els at %arious

coastal locations$ The simulated le%els are compared to those that can be e)tracteddirectly from 2-/'P 9tidal constituents only:$ 's seen there is a good agreement$ The

model results, ho&e%er, also include the set-up from &ind and pressure fields and are

thus more representati%e for the actual conditions$

'


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Summer conditions Winter conditions

Banuary !""8-( /ay !""8 9strong ?a 4i>a e%ent: Buly !""; - ( 4o%ember !""; 9&eak 0l 4i>o e%ent:

+igure .-( through +igure .-(8 sho& the results for Banuary through /ay !""8, &hich

is a ?a 4i>a summer e%ent$ =t is obser%ed that the model succeeds in modelling a clear

south&ard ad%ection of &arm euatorial surface &ater from the northern part of the

domain and a re-bounce to the initial standard situation &ith north and north&est&ard

ad%ection of cold up&elling &ater$ ' particularly con%incing %alidation plot is the

transient south&ard ad%ection of the &arm euatorial &ater in figure .-; 9!; +ebruary

!""8:$

+igure .-(; through +igure .-3 sho& the results for Buly through 4o%ember !"";,

&hich is a &eak 0l 4i>o &inter e%ent$ ' robust de%elopment of the ad%ection patterns is

obser%ed in this period$


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Figure 6-1% #imulated !ertical temperature structure on >an-27 1288: 2887 #ummer .l /ino (see alsoFigure ;-5)

6,2 rill "uttings

Pending

6,3 ud spills

Pending

6,3,1 eposition of fine particles

Pending

6,3,2 #oluble toic substancesPending

6,% racking of oil spill

Pending

15%78753,doc 15 9'


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< @eferences

*1* Pe%en P, E$ 0che%in, B$ Pasapera, +$ 2olas, B$ Tam, !""5$ '%erage circulation cycle, andmesoscale dynamics of the Peru 2urrent #ystem ' model approach$ Bournal of

Deophysical research$ Eol ((", 92(":, !""5$

7!7 2rouette, /$, D$ 0ldin, and E$ 0che%in, !""@ n the 2ontributions of 0kman

Transport and Pumping to the


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a p p e n d i

.cotoicological data of cemicals in +ater based mud9Pending:

115%78753,doc -1


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a p p e n d i b

&.LL'/4 @.#AL#

11807609-oil spill block 35-36-draft report

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